314 



COMPARATIVE ANATOMY 



CHAT. 



SUB-CLASS 3. Blastoidea. 



Armless Pelmatozoa, either pear-shaped, club-shaped, oviform, or spherical. 

 Body usually regularly radiate. Base mouocyclic. Three basals, one small and 



i 2 



1 '!;. -2t\3. Pentremites, from 

 the side, without pinnules. 1, 

 Intel-radial ^deltoid ; '_', 3, radials ; 

 4, basal ; 5, ambulacrum : r>. spir- 

 acle. 



!'[.. 2i - >">. Cadaster toilobatus, M'Coy, from the oral 

 side (after Etheridge and Carpenter). 1, Hydrospire 

 slits; _', lateral plates; 3, anibulacral groove; 4, mouth : 

 .", radial ; '.. suture between two radials; 7, anus; 8, inter- 

 radial ; '.'. ridi^e on an interradial. 



Fio. 264. Granatocrinus Norwood! 

 (after Etheridge and Carpenter): from F IG . 266.-Orophocrinus stellifonnis (after Ethe- 



the apical side, with stem. "dge and Carpenter) ; from the oral side. 1 Lateral 



plates ; 2, covering plates of the ambulacra ; 3, liydro- 

 spire slits ; 4, anus ; f>. anibulaeral groove ; 6, points 

 of attachment of the pinnules. 



two larger. Five radials, more or less deeply cut out for the reception of the live 

 ambulacra. Five interradials lying above the five radials, and surrounding the 



